In the original round-robin differential-phase-shift (RRDPS) quantum key
distribution and its improved method, the photon-number-resolving detectors are
must for the security. We present a RRDPS protocol with yes-no detectors only.
We get the upper bounds of mutual information of Alice and Eve, and Bob and
Eve, and the formula of key rate. Our main idea is to divide all counts into
two classes, the counts due to the odd number photons of incident detectors and

We propose a novel type of composite light-matter interferometer based on a
supersolid-like phase of a driven Bose-Einstein condensate coupled to a pair of
degenerate counterpropagating electromagnetic modes of an optical ring cavity.
The supersolid-like condensate under the influence of the gravity drags the
cavity optical potential with itself, thereby changing the relative phase of
the two {cavity electromagnetic fields}. Monitoring the phase evolution of the

Usually the influence of the quadratic Stark effect on an ion's trapping
potential is minuscule and only needs to be considered in atomic clock
experiments. In this work we excite a trapped ion to a Rydberg state with
polarizability $\sim$~eight orders of magnitude higher than a low-lying
electronic state; we find that the highly-polarizable ion experiences a vastly
different trapping potential owing to the Stark effect. We observe changes in
trap stiffness, equilibrium position and minimum potential, which can be tuned

Exceptional points, resulting from non-Hermitian degeneracies, have the
potential to enhance the capabilities of quantum sensing. Thus, finding
exceptional points in different quantum systems is vital for developing such
future sensing devices. Taking advantage of the enhanced light-matter
interactions in a confined volume on a metal nanoparticle surface, here we
theoretically demonstrate the existence of exceptional points in a system
consisting of quantum emitters coupled to a metal nanoparticle of subwavelength

The equivalence principle in combination with the special relativistic
equivalence between mass and energy, $E=mc^2$, is one of the cornerstones of
general relativity. However, for composite systems a long-standing result in
general relativity asserts that the passive gravitational mass is not simply
equal to the total energy. This seeming anomaly is supported by all explicit
derivations of the dynamics of bound systems, and is only avoided after
time-averaging. Here we rectify this misconception and derive from first

We review several no-go theorems attributed to Gisin and Hardy, Conway and
Kochen purporting the impossibility of Lorentz-invariant deterministic
hidden-variable model for explaining quantum nonlocality. Those theorems claim
that the only known solution to escape the conclusions is either to accept a
preferred reference frame or to abandon the hidden-variable program altogether.
Here we present a different alternative based on a foliation dependent
framework adapted to deterministic hidden variables. We analyse the impact of

Single quantum light-emitters are valuable resources for engineered quantum
systems. They can function as robust single-photon generators, allow optical
control of single spins, provide readout capabilities for atomic-scale sensors,
and provide interfaces between stationary and flying qubits. Environmental
factors can lead to single emitters exhibiting "blinking", whereby the
fluorescence level switches between on and off states. Detailed
characterisation of this blinking behaviour including determining the switching

In a breakthrough, Hastings' showed that there exist quantum channels whose
classical capacity is superadditive i.e. more classical information can be
transmitted by quantum encoding strategies entangled across multiple channel
uses as compared to unentangled quantum encoding strategies. Hastings' proof
used Haar random unitaries to exhibit superadditivity. In this paper we show
that a unitary chosen uniformly at random from an approximate $n^{2/3}$-design

We report the first demonstrations of both quadrature squeezed vacuum and
photon number difference squeezing generated in an integrated nanophotonic
device. Squeezed light is generated via strongly driven spontaneous four-wave
mixing below threshold in silicon nitride microring resonators. The generated
light is characterized with both homodyne detection and direct measurements of
photon statistics using photon number-resolving transition edge sensors. We

Parity-Time (PT) symmetric quantum mechanics is a complex extension of
conventional Hermitian quantum mechanics in which physical observables possess
a real eigenvalue spectrum. However, an experimental demonstration of the true
quantum nature of PT symmetry has been elusive thus far, as only
single-particle physics has been exploited to date. In our work, we demonstrate
two-particle quantum interference in a PT-symmetric system. We employ
integrated photonic waveguides to reveal that PT-symmetric bunching of